1. Field of the Invention
The present invention generally relates to a surgical stapling instrument for applying surgical staples to tissue and, more particularly, to a surgical stapling instrument for performing a circular anastomosis stapling operation. More specifically, this invention relates to a surgical instrument in which a stapling head assembly is mounted by a curved shaft to an actuator handle assembly and to an improved actuator mechanism for transmitting the required operating forces and movements from the actuator handle assembly through the curved shaft to the stapling head assembly. Also, this invention relates to an improved stapling head assembly provided with a detachable anvil and a retractable staple driver. Further, this invention concerns an improved actuator mechanism which permits adjustment of the anvil gap to produce a desired staple height and precludes actuation of the stapling head assembly if the anvil gap is outside of a predetermined range.
2. Description of the Prior Art
The field of surgical stapling has seen substantial advances in the past decades. Specifically, in the area of internal anastomotic stapling the advances have been quite dramatic. Devices such as the Proximate.TM. ILS stapler, produced by the assignee of the present invention, Ethicon, Inc., Somerville, N.J., have enabled surgeons to perform operations and procedures which were heretofore perceived as difficult, if not impossible, with relative ease.
Generally, in the performance of a surgical anastomotic stapling operation, two pieces of lumen or tubular tissue, e.g., intestinal tissue, are attached together by a ring of staples. The two pieces of tubular tissue may be attached end to end or one piece of tubular tissue may be attached laterally around an opening formed in the side of another piece of tubular tissue. In performing the anastomosis with a stapling instrument, the two pieces of tubular tissue are clamped together between an anvil provided with a circular array of staple forming grooves and a staple holder provided with a plurality of staple receiving slots arranged in a circular array in which the staples are received. A staple pusher is advanced to drive the staples into the tissue and form the staples against the anvil. Also, a circular knife is advanced to cut the excess tissue clamped between the anvil and the staple holder. As a result, a donut-shaped section of tissue is severed from each lumen and remains on the anvil shaft. The tubular tissue joined by the circular ring of staples is unclamped by advancing the anvil shaft distally to move the anvil away from the staple holder. The stapling instrument is removed by pulling the anvil through the circular opening between the pieces of tubular tissue attached by the ring of staples.
In the prior art, several types of circular anastomosis stapling instruments are known. For example, U.S. Pat. Nos. 4,576,167 and 4,646,745 to Noiles disclose a surgical stapler in which a stapling assembly is connected by an elongated shaft assembly having a longitudinally curved section to an actuator assembly. The shaft assembly includes an articulated hollow tube and a flexible band inside the tube, which are coaxial with a curved section of a hollow support shaft, for transmitting the compression and tension forces required to operate the stapling assembly. The hollow compression tube is concentric with the hollow support shaft. The flexible tension band is disposed in the interior of the hollow compression tube. Two elongated flexible spacer elements are mounted inside the compression tube above and below the flexible tension band to maintain the tension band substantially in the center of the curved compression tube. The compression tube and the tension band are mounted coaxial with respect to the curved sections of the support shaft.
It is also known in the prior art to provide a circular anastomosis stapling instrument including a flexible shaft which allows the stapling head to assume various orientations relative to the actuator assembly. Examples of circular stapling instruments with flexible shafts are disclosed in Noiles et al U.S. Pat. No. 4,473,077, Barker et al U.S. Pat. No. 4,754,909, and Shichman U.S. Pat. No. 4,488,523.
European Patent Application No. 293,123-A2 discloses a surgical anastomosis stapling apparatus including a stapling assembly comprising a tubular housing which supports an annular array of staples, a staple pusher mounted for movement between a retracted position within the housing and an extended position for expelling the annular array of staples, and a cylinder slidably mounted within the pusher assembly for selectively mounting either a trocar or an anvil assembly. The cylinder includes a central bore at its distal end for receiving a solid anvil shaft which is releasably held in the central bore by a detent formed on a spring member mounted at the distal end of the cylinder. The anvil shaft includes external longitudinal splines which engage internal splines provided within the housing for aligning the anvil shaft with the housing.
Co-pending U.S. application Ser. No. 590,404, filed Sep. 28, 1990, by Main and assigned to Ethicon, Inc., discloses a surgical stapling device including an anvil portion which is detachable from a stapling head portion containing a trocar tip upon which the anvil is attached. The anvil portion contains an elongated sleeve with an opening through which the trocar tip is inserted. The anvil is provided with a locking clip which releasably engages an indentation or ridge provided on the trocar tip which allows the anvil to be separated from the trocar tip.